Recently, in the art of rotors, techniques in which a permanent magnet is inserted into a hole portion provided in a rotor core and a liquid resin is filled between the hole portion and the permanent magnet to fix the permanent magnet to the rotor core have been used. In such a technical field, a urethane resin, an epoxy resin, and the like are usually employed as a liquid resin. This technology is described in, for example, Patent Document 1.
Furthermore, in Patent Document 2, an epoxy resin for encapsulating a motor, which is used for encapsulating a motor, and a molded article formed by curing the same are described. It is described that working environment properties, productivity, heat resistance, heat conductivity, solvent resistance, high humidity water resistance, and a low linear expansion coefficient are attained in the molded article. For this reason, it is thought that the molded article described in Patent Document 2 is used for a housing of a motor.
Moreover, the rotor described in Patent Document 3 has a structure where a second hole portion communicating with a first hole portion and positioning along the rotation direction of the rotor is formed on the side of the first hole portion accommodating a permanent magnet. By filling a resin or disposing a spring in the second hole portion, a stress that the permanent magnet gets from the side wall of the first hole portion in the rotation direction of the rotor is reduced, which is described to be capable of preventing cracking of the permanent magnet. In the same document, it is described that an epoxy resin that is filled with silica can be employed as a resin, but any specific amounts of silica filled is not described. In addition, in the same document, a technique for filling a resin in a hole portion has not been described.
Incidentally, as a technique for filling a liquid resin between the hole portion and the magnet of the rotor core, there exist two techniques, a first-in technique and a coating technique. The first-in technique has the following steps. First, a liquid resin is filled into a hole portion of a rotor core by a dispenser. Thereafter, a magnet is inserted into the hole portion filled with the liquid resin. The first-in technique is described in Patent Documents 4 and 5. On the other hand, the coating method has the following steps. First, the magnet is coated with the liquid resin with a brush. The magnet coated with the liquid resin is inserted into the hole portion of the rotor core. The coating method is described in Patent Document 6.